Evening Flurries

December 9, 2013

10pm Monday…

Some excitement out there the past couple hours as a few light snow flurries moved through the metro area.  Looks like the last batch is moving through East Vancouver.  Enough to give a good coating on the ground in a few spots.  I see I-205 is partially covered by fresh snow and slower moving traffic up around SR 500 on the WADOT video feed.

Radar looks pretty dry the next couple of hours…again, real light stuff.

So far it appears to be all snow, but the temperature at the top of our KPTV transmission tower in the West Hills (1800′) has come up to just under freezing.  A good indication of warming up above the surface overnight.  Thus the increasing chance for some spots of freezing drizzle or freezing rain showers.

We just had our first report of freezing rain in Sheridan at 10pm.

Otherwise evening models were no different, not a whole lot of moisture.  Best chances for more than 1/2″ of snow or significant freezing rain is north and west of the metro area.  And NE up in Clark County too.

Chief Meteorologist Mark Nelsen


Monday PM Update: Looking a Little Drier

December 9, 2013

2:45pm…

We just had a flurry pass through the west side of the metro area, one of those “green” spots on the radar I mentioned on the previous post.

I’ve looked through several more model runs, stared at the radar screen a few times, and have a few thoughts:

1. Many of us will stay dry tonight through Thursday morning, thus in those areas no commuting issues Tuesday morning

Take a look at the WRF-GFS rainfall accumulation map through 4am tomorrow.  Little or nothing for most of the metro area and anywhere south into the valley:

oc_pcp24.24.0000

And a wider view showing anything that might fall after 4am.  A few hundredths of an inch.  If it was rain, we’d say a few sprinkles or a light shower later tonight or Tuesday morning:

or_pcp48.48.0000

and our RPM…totally dry!

RPM_12KM_Precip_NWOR

2. The coast is pretty much done with frozen precipitation.  Temps have warmed above freezing everywhere except where a light easterly flow is coming down the Columbia River.  Even that will gradually warm tomorrow morning.  Yes, still some icy streets around Astoria possible overnight.

3.  Very spotty snow flurries, with a dusting or so, are possible at some point this evening through the Tuesday morning commute inland, mainly from Portland north.  I think a lot of us will just wake up to flurries or a dusting on the ground.  Others could see up to 1/2″ or so in the eastern part of Clark County (Battle Ground, Hockinson, Camas) and eastern Multnomah County (Troutdale, Gresham, Corbett).  Plus Vernonia, Banks, St. Helens, and Scappoose.  The best spot could be up at Kelso and Longview where there will be a little more moisture.

4. A bigger issue is that areas of freezing drizzle or freezing rain showers could develop instead of or with flurries.  That’s because slightly warmer air is moving in around 2,000-3,000′ up.  It only takes a few minutes of liquid drizzle or rain to coat a road and make it an ice rink; far more dangerous & destructive than a half-inch of snow.

5.  Best areas for frozen precipitation of any sort away from the Cascade foothills?  Higher terrain north and west of downtown Portland (West Hills, Columbia County, Cowlitz County, Kelso/Longview)

IF we get more precipitation than expected, especially if it’s freezing rain, roads will be a huge mess for the Tuesday morning commute.  NO ROADS WEST OF THE CASCADES WILL THAW UNTIL SOMETIME TUESDAY.  If a road looks wet, it’s icy.  Stay tuned here, on FOX12 (starts at 4:30am!) or on our Facebook/Twitter pages.  We are FOX12WEATHER on both of those.

I’ll do another update later this evening if conditions warrant…but for now I’ve run out of text colors to use, so I’ll sign off.

Chief Meteorologist Mark Nelsen


Monday Morning Update: Flurries This Afternoon/Evening

December 9, 2013

10am Monday…

Sure FEELS like snow doesn’t it?

Solid cloud cover moved in the past few hours; it’s not going anywhere until Tuesday evening.  We are done with nights in the teens and single digits.  Now we begin a very slow moderation of the arctic air mass over us.  At the same time, northwesterly and westerly wind around 2,000′ and above is pushing moisture onto the coast and inland.  Light snow has been falling north of Tillamook and up onto the Washington coastline this morning.  Nothing except flurries is making it over the Coast Range…too dry.  This will continue the next few hours.  Thus another cold day with solid gray skies.

A weak disturbance passing overhead will squeeze flurries or freezing rain/drizzle out of the cloud layer this evening through Tuesday morning, then it’s back to dry until sometime Thursday.  All the previous bullet points on last night’s post are still valid, if you didn’t read those, you should.

So for this evening’s commute, at worst I expect flurries with only a dusting with little or no effect on roads.  There, I said it; now we’ll see what happens.  At best it’ll just be dry.  That includes the Portland metro area up to Woodland or so along I-5.  I think there’s a better chance for a half-inch or less snowfall north of St. Helens on the Oregon side of the Columbia and north of Woodland (Kelso/Longview) at some point this evening.

The main chance for frozen precipitation appears to be later tonight and for Tuesday morning’s commute, with the best chance up against the Cascade foothills in Clark and Multnomah counties.  This is very similar to the drizzle setup we often get where the metro area is mainly dry but it drizzles or rains lightly on the far east side of town and into the foothills.  Those spots could see an inch or more.

Today is a good “radar-watching” day.  Here is a link to Portland’s:  http://weather.cod.edu/satrad/nexrad/index.php?type=RTX-N0Q-1-12

and the Washington Coast radar:  http://weather.cod.edu/satrad/nexrad/index.php?type=LGX-N0Q-1-12

You generally need echoes above 10dbz (GREEN) to get precipitation down to ground level.  That said, this evening and overnight some of the precipitation will be below the radar beam, so the radar may show nothing and it’ll be snowing at your house.

Chief Meteorologist Mark Nelsen